In the case of attaching and using an ultrasonic sensor to a bottom surface of a fuel tank for a vehicle in order to measure a level of a fuel in the fuel tank for a vehicle, the ultrasonic sensor is not exposed to the outside (air), such that an error of the ultrasonic sensor itself may be minimized, but it is difficult to measure a level of a fuel existing in a blind zone overlapping a ringing time generated at the time of driving the ultrasonic sensor.
In addition, in the case in which the fuel in the fuel tank for a vehicle reaches a temperature of a boiling point or more depending on an external environment, the fuel is boiled, such that bubbles are generated, as illustrated in FIG. 1.
In this case, when an ultrasonic signal for measuring a distance up to a fuel surface is transmitted using the ultrasonic sensor in order to measure a liquid level of the fuel in the fuel tank for a vehicle, a scattered reflection or scattering phenomenon due to the bubbles occurs.
In the case in which the scattered reflection or scattering phenomenon due to the bubbles occurs as illustrated in FIG. 1, the reflected ultrasonic signal may not be received, such that it is recognized that the fuel does not exist. Therefore, it is difficult to measure an accurate liquid level.
Korean Patent Laid-Open Publication No. 10-1999-0058443 (entitled “Fuel Amount Measuring Device and Method Using Ultrasonic Sensor” and referred to as Related Art Document 1) discloses a fuel amount measuring device and method capable of calculating a fuel amount remaining in a fuel tank by measuring a distance up to a fuel surface using an ultrasonic sensor installed on an inner wall of the fuel tank.
However, Related Art Document 1 does not mention a method for solving a problem that it is difficult to measure a level of a fuel existing in a blind zone overlapping a ringing time generated at the time of driving the ultrasonic sensor or a method for overcoming a measuring error of the ultrasonic sensor in the case in which the fuel is boiled, such that the bubbles are generated, which is the problem described above.